1. Field of the Invention
This invention relates to a navigation control system and particularly for a current position recognition system for a mobile robot, and more particularly to such a system which enhances visual recognition processing speed and accuracy in a mobile robot which recognizes distinctive or characteristic shapes in its navigation environment which are suitable for a visual recognition algorithm and recognizes its own current position from the position of the recognized shapes.
2. Description of the Prior Art
Mobile robots have been proposed in a wide range of types, including the legged type taught by Japanese Laid-Open Patent Publication No. 62(1987)-97,005, the crawler type taught by Japanese Laid-Open Patent Publication No. 62(1987)-285,112, and the wheeled type. It is considered that such mobile robots can be designed to move while keeping track of their current position by visual recognition of the images of surrounding objects which are easy to see and of simple shape. During navigation indoors, such objects would include the ceiling and doors, for example. Visual recognition technologies are discussed in detail in, for example, "Machinery Research" Vol 43, No. 1 (1991) and "Journal of Japanese Society for Artificial Intelligence" Vol. 5, No. 6 (Nov. 1990).
In order to navigate through a complex environment, a mobile robot has to be able to ascertain its current position with high accuracy. A method which attempts to ascertain the current position from an object like a ceiling which is distant and whose position is hard to measure accurately is incapable of enabling an acceptable degree of navigation precision.
The obvious solution to this problem is to select nearby objects whose shapes are easy to recognize as the references for ascertaining current position with high accuracy. The problem with this approach, however, is that the objects within the navigation environment which have shapes etc. suitable for visual recognition provide such a large number of labels (features such as corners and colors) that it is difficult to select the features to be used unless they are defined in advance or the path to be navigated is specified beforehand.